Trends and determinants of taking tetanus toxoid vaccine among women during last pregnancy in Bangladesh: Country representative survey from 2006 to 2019

Background Tetanus occurring during pregnancy is still an important cause of maternal and neonatal mortality in developing countries. This study estimated the trend of tetanus toxoid (TT) immunization coverage from 2006 to 2019 in Bangladesh, considering socio-demographic, socio-economic, and geospatial characteristics. Methods The dataset used in this study was extracted from Multiple Indicator Cluster Surveys (2006, 2012–13, and 2019) including 28,734 women aged between 15–49 years. Data analysis was performed using cross-tabulation and logistic regression methods. Further, the spatial distribution of TT immunization coverage was also depicted. Results The trend of TT immunization (81.8% in 2006 to 49.3% in 2019) and that of taking adequate doses of TT (67.1% in 2006 to 49.9% in 2019) has gradually decreased throughout the study period. Among the administrative districts, North and South-West regions had lower coverage, and South and West regions had relatively higher coverage of both TT immunization and that of adequate doses. Antenatal TT immunization (any dosage, inadequate or adequate) was significantly associated with lower age (AOR = 3.13, 1.55–6.34), higher education (AOR = 1.20, 1.03–1.40), living in urban areas (AOR = 1.17, 1.03–1.34), having immunization card (AOR = 5.19, 4.50–5.98), using government facilities for birth (AOR = 1.41, 1.06–1.88), and receiving antenatal care (ANC) (AOR = 1.51, 1.35–1.69). In addition, living in urban areas (AOR = 1.31, 1.10–1.55), having immunization cards (AOR = 1.62, 1.36–1.92), and choosing others’ homes for birth (AOR = 1.37, 1.07–1.74) were significantly associated with adequate TT immunization. However, higher education (AOR = 0.57, 0.44–0.74), having poor wealth index (AOR = 0.65, 0.50–0.83), and receiving ANC (AOR = 0.76, 0.63–0.92) had lower likelihood of taking adequate TT immunization. Conclusions The gradual decline in the TT immunization rate in the present study suggests the presence of variable rates and unequal access to TT immunization, demanding more effective public health programs focusing on high-risk groups to ensure adequate TT immunization.

a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 year of age and 52% of reproductive age took at least one TT immunization. Furthermore, 85% of mothers with children under one year old, 64% of married women who had previously been pregnant, and 47% of women of reproductive age reported receiving at least two doses of TT vaccination [24]. Another study depicts that only 22.3% of pregnant women took one TT and 56.3% had more than 2 TT immunizations [25]. In addition, Abir et al. from Bangladesh reported that 26.0% of mothers had taken one TT dose, and 55.6% had received two or more doses [26]. These studies did not investigate the trends of TT coverage over the years, which is the focus of the present study.
Notably, after India, China, and Pakistan; Bangladesh was identified as the fourth-highest country for neonatal tetanus with estimated cases of 41000 annually [23]. Vulnerability in pregnant women mostly resides in the rural part of our country where TT is a continuing program under EPI regarding maternal and neonatal tetanus elimination. Bangladesh government has taken the initiative of the EPI program since 7th April 1979 [27]. However, to our knowledge, changes over time in TT vaccination coverage have not been investigated. Little is known about the determinants of TT vaccination coverage in Bangladesh, a country being a hotspot for infectious diseases. Better understanding the determinants of TT vaccination coverage may also assist in tailoring program interventions. Therefore, it is important to understand the general trend of TT vaccination coverage, and the issues surrounding vaccination. This study aims to demonstrate the trend and determinants of TT immunization among Bangladeshi pregnant women using data from the United Nations Children's Fund (UNICEF) from 2006 to 2019.

Data overview
This cross-sectional study used survey data sets from 2006, 2012-13, and 2019 of the Bangladesh Multiple indicator cluster surveys (MICS), an international survey initiative carried out by the Bangladesh Bureau of Statistics in collaboration with UNICEF. The MICS were developed and supported by UNICEF "focusing mainly on issues that directly affect the lives of children and women" allowing countries to generate evidence and recommended strategies to monitor the progress toward millennium development goals [28]. The survey (2019) employed a two-stage stratified cluster sampling method where each of the 64 districts was considered as the sampling strata. The primary sampling units were enumeration areas (EAs) based on the 2011 Bangladesh population, with housing census and households serving as secondary sampling units. Using the probability proportional to size (PPS) method, a total of 3220 EAs were selected from all 64 strata in the first step of sampling. In the second stage, a random systematic selection was utilized to choose a sample of 20 households from each sampled EA [29]. For the 2012-13 round, a two-stage stratified cluster sampling approach was used to determine the survey samples. Administrative districts were designated as priority districts and non-UNDAF districts under the United Nations Development Assistance Framework (UNDAF). 50 sample clusters were chosen from each of the 20 UNDAF districts, and 40 sample clusters were chosen from each of the 44 non-UNDAF districts. A systematic random selection technique was used to choose sample households in each cluster from a list of households [30]. In round 2006, a multi-stage, stratified cluster sampling approach was used for the selection of the survey sample. In each enumeration region, households were sequentially numbered from 1 to 100 (or more), and 35 households were selected using systematic selection procedures [31]. We extracted data for women aged 15-49 years from the dataset of three rounds of the survey. The total number of households surveyed from 2006 to 2019 was 206568. In the raw data, the total number of women aged 15-49 years was 186028 (unweighted). After cleaning the missing values, the remaining 11812, 7783, and 9139 (weighted) women from 2006, 2012-13, and 2019, respectively were included in the final analysis.

Outcome variables
The two outcome variables used for this study were similar to previous studies [13,18,19]. The question that was asked to the participants was whether or not they took TT vaccination during their last pregnancy. In addition, based on WHO recommendations, receiving at least two doses of TT is considered adequate while less than 2 doses are regarded as inadequate [19].

Statistical analyses
IBM SPSS statistics 26.0 version was used for the analysis. First, simple descriptive tests were done to observe the exact group frequencies, percentages, minimum, maximum, range, etc. Then, Pearson Chi-square tests were carried out to imprint the association of covariates with the two dependent variables. Multicollinearity between independent variables was measured using correlation coefficient and the value of all the variables was less than 0.5 indicating the absence of multicollinearity. After that, logistic regression models for the binary outcome were used to analyze the multivariable association between covariates and outcomes. Tableau Desktop version 2021.2 was used to create the line chart and ArcGIS v10.5 to visualize the % changes occurring across 64 districts of Bangladesh. All tests were two-sided and had statistically eligible significant values below 0.05 with 95% confidence intervals. Forest plots were used for the graphical representation of the significant findings.

Ethical clearance
This study analyzed survey data from UNICEF, where all the personally identifiable information of participants had been removed. The national statistical office, Bangladesh Bureau of Statistics, and UNICEF obtained informed consent from survey participants before their participation. Because we used publicly available de-identified data, our work was exempt from full ethical review process and approved by the Research and Ethical Committee of Department of the Biochemistry and Food Analysis, Patuakhali Science and Technology University (approval no.: BFA 12/01/2022:03). In addition, upon completing the registration process, the authors were granted permission to download and use the datasets. The data are available online: http://mics.unicef.org/surveys.

Changes in the prevalence of taking tetanus toxoid in Bangladesh
After excluding the missing values, 28,734 pregnant women aged 15-49 years were included in our study (Fig 1). As shown in Fig Table 1

Determinants of taking adequate tetanus toxoid vaccine in Bangladesh
The education of the participant is a significant covariate of adequate TT immunization. This data demonstrates that in 2006 and 2012-13, the women who did not complete their secondary education had significantly lower (AOR = 0.80, 0.70-0.91) and (AOR = 0.77, 0.63-0.95) uptake of adequate TT doses than uneducated women (Fig 5, S2 and S4 Tables). Similarly, the women who completed secondary or higher education had significantly lower (AOR = 0.57, 0.44-0.74) and (AOR = 0.70, 0.54-0.91) TT immunization in the 2012-13 and 2019 survey years than those who never attended school. In addition, the study results disclosed that the odds of utilizing adequate TT immunization were significantly higher in urban areas than in    [36] showed that sufficient TT immunization among pregnant women was 75% worldwide, 95% in South East Asia, 63% in Africa, and 53% in East Mediterranean. The high socio-demographic condition is associated with TT immunization. The higher TT immunization rate among younger women in the present study might be attributed to the improved formal female education and access to modern media outlets. By previous studies, age is an insignificant factor regarding adequate doses of TT immunization [13]. In contrast, the association between age and adequate doses of TT immunization has been demonstrated in other countries [18,19]. However, we determined that age is a significant factor regarding any doses of TT immunization only for 2012-13 and 2019. Further studies are warranted to comprehend this connection properly. With some exceptions, this study suggests that increasing the level of education increases the uptake of TT immunization and adequate doses of TT immunization, in line with other studies [37,38]. Because educated women might be more likely to have decision-making power regarding their health and education may improve the level of knowledge about the deleterious effects of tetanus [18]. In our study, urban women were more likely to take sufficient TT immunization, in agreement with other studies [39,40], which might reflect the improved access to healthcare facilities in the urban area. Therefore, interventions especially targeting uneducated rural women are needed to improve the current scenario of TT immunization in Bangladesh. However, another study in Afghanistan concluded that urban women had lower odds of being sufficiently vaccinated, and may be offered less TT immunization than their rural counterparts due to less knowledgeable ANC providers and less vaccine availability [41].
Bangladesh has achieved remarkable health improvements during the last two decades [42]. More recently, Bangladesh was commended as an example of "good health at low cost" [42]. However, socioeconomic inequality in health, especially in maternal and child mortality remains a disturbing reality in Bangladesh [42]. Similar to our findings, studies revealed that increasing the wealth index of women in the household is protective against tetanus compared to a poor wealth index [18]. The financial reason might contribute to women from wealthy households getting easier access to healthcare facilities compared to those from poor households as well as women from low economic status are challenged with availability and high maternity and transportation cost when seeking health care. Moreover, women from the poor wealth index might be engaged in other activities to fulfill their basic needs, limiting their time to utilize healthcare services compared with the richest suggesting that strategies such as improvement of health literacy and logistic support could be taken to enable coverage and equity of TT immunization across women on areas with poor wealth index. However, this finding opposes a study conducted in the Gambia that showed that the wealth quintile did not affect TT immunization [19].
This study showed that women who uptake TT immunizations or adequate TT doses using immunization cards had a higher chance of being protected from tetanus. This finding is similar to studies conducted in Ethiopia and Ghana [22,43], which encouraged women to promote immunization card retention as well as other records of health facilities as a mechanism to improve the immunization rate. The present study demonstrated that birth at government facilities and home birth were protective factors for TT immunization and adequate TT doses. The presence of user fees for maternal health services and immunization might appear to be a major barrier to increasing TT immunization in private clinics suggesting exemption of user fees for maternal and child immunization [44,45]. However, the current study contradicts the findings of an earlier study [46] that showed that place of delivery did not affect TT immunization.
Another important factor significantly associated with TT immunization was ANC followup, consistent with previous studies conducted in different countries worldwide [13,18]. This might be because higher ANC follow-up increased awareness of the importance of TT immunization and ANC visits also offer interventions and provides critical healthcare functions that might be crucial to health and well-being. Interestingly, women who attend high ANC visits are less likely to receive adequate TT immunization. This suggests that the burden of user fees and transportation costs for ANC might serve as a barrier to care and further discourage the continuation of TT immunization, contributing to the evidence that user fees exemption policies may reduce the inequities in access to care [47].
The spatial analysis discovered some district-wise variations in the change rate of TT immunization from 2006 to 2019, with Rangamati and Bandarban districts experiencing the worst. Moreover, regarding adequate TT doses, the situation was worse in Bandarban, Cox's Bazar, Pabna, Natore, Thakurgaon, and Nilphamari districts. Therefore, the policy focus here would be on the peripheral districts and the hill tracts in Bangladesh to improve women's health literacy in remote areas and ensure maternal healthcare access.
This study has several strengths. First, this is the first study to demonstrate trends of TT immunization among women during the last pregnancy in Bangladesh. Second, we used data from three nationally representative datasets and the findings can be generalized to a whole nation. However, this study does have some limitations. Due to the cross-sectional nature of the study, causal inference of the association between TT immunization and women's health cannot be drawn. Since this study asks participants about past exposure and numerous vaccines indicated in the period in question, recall bias may occur. Social media exposure variables like watching television, using a computer, and listening to radiofrequency were not common in the three datasets and are missing from the analysis. Secondary data used in the analysis allowed us to lack control over the variables of interest to include in the analysis.